Added unique operator

pkg/yqlib/doc/Unique.md

@@ -0,0 +1,82 @@
+This is used to filter out duplicated items in an array.
+
+## Unique array of scalars (string/numbers)
+Given a sample.yml file of:
+```yaml
+- 1
+- 2
+- 3
+- 2
+```
+then
+```bash
+yq eval 'unique' sample.yml
+```
+will output
+```yaml
+- 1
+- 2
+- 3
+```
+
+## Unique nulls
+Unique works on the node value, so it considers different representations of nulls to be different
+
+Given a sample.yml file of:
+```yaml
+- ~
+- null
+- ~
+- null
+```
+then
+```bash
+yq eval 'unique' sample.yml
+```
+will output
+```yaml
+- ~
+- null
+```
+
+## Unique all nulls
+Run against the node tag to unique all the nulls
+
+Given a sample.yml file of:
+```yaml
+- ~
+- null
+- ~
+- null
+```
+then
+```bash
+yq eval 'unique_by(tag)' sample.yml
+```
+will output
+```yaml
+- ~
+```
+
+## Unique array object fields
+Given a sample.yml file of:
+```yaml
+- name: harry
+  pet: cat
+- name: billy
+  pet: dog
+- name: harry
+  pet: dog
+```
+then
+```bash
+yq eval 'unique_by(.name)' sample.yml
+```
+will output
+```yaml
+- name: harry
+  pet: cat
+- name: billy
+  pet: dog
+```
+

pkg/yqlib/doc/headers/Unique.md

@@ -0,0 +1 @@
+This is used to filter out duplicated items in an array.

pkg/yqlib/expression_tokeniser.go

@@ -259,6 +259,8 @@ func initLexer() (*lex.Lexer, error) {
 	lexer.Add([]byte(`sortKeys`), opToken(sortKeysOpType))
 	lexer.Add([]byte(`select`), opToken(selectOpType))
 	lexer.Add([]byte(`has`), opToken(hasOpType))
+	lexer.Add([]byte(`unique`), opToken(uniqueOpType))
+	lexer.Add([]byte(`unique_by`), opToken(uniqueByOpType))
 	lexer.Add([]byte(`explode`), opToken(explodeOpType))
 	lexer.Add([]byte(`or`), opToken(orOpType))
 	lexer.Add([]byte(`and`), opToken(andOpType))

pkg/yqlib/lib.go

@@ -99,6 +99,8 @@ var recursiveDescentOpType = &operationType{Type: "RECURSIVE_DESCENT", NumArgs:
 
 var selectOpType = &operationType{Type: "SELECT", NumArgs: 1, Precedence: 50, Handler: selectOperator}
 var hasOpType = &operationType{Type: "HAS", NumArgs: 1, Precedence: 50, Handler: hasOperator}
+var uniqueOpType = &operationType{Type: "UNIQUE", NumArgs: 0, Precedence: 50, Handler: unique}
+var uniqueByOpType = &operationType{Type: "UNIQUE_BY", NumArgs: 1, Precedence: 50, Handler: uniqueBy}
 var deleteChildOpType = &operationType{Type: "DELETE", NumArgs: 1, Precedence: 40, Handler: deleteChildOperator}
 
 type Operation struct {

pkg/yqlib/operator_unique.go

@@ -0,0 +1,59 @@
+package yqlib
+
+import (
+	"github.com/elliotchance/orderedmap"
+	"container/list"
+	yaml "gopkg.in/yaml.v3"
+	"fmt"
+)
+
+func unique(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+	selfExpression := &ExpressionNode{Operation: &Operation{OperationType: selfReferenceOpType}}
+	uniqueByExpression := &ExpressionNode{Operation: &Operation{OperationType: uniqueByOpType}, Rhs: selfExpression}
+	return uniqueBy(d, context, uniqueByExpression)
+
+}
+
+func uniqueBy(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+
+	log.Debugf("-- uniqueBy Operator")
+	var results = list.New()
+
+
+	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
+		candidate := el.Value.(*CandidateNode)
+		candidateNode := unwrapDoc(candidate.Node)
+
+		if candidateNode.Kind != yaml.SequenceNode {
+			return Context{}, fmt.Errorf("Only arrays are supported for unique")
+		}
+		
+		var newMatches = orderedmap.NewOrderedMap()
+		for _, node := range candidateNode.Content {
+			child := &CandidateNode{Node: node}
+			rhs, err := d.GetMatchingNodes(context.SingleChildContext(child), expressionNode.Rhs)
+
+			if err != nil {
+				return Context{}, err
+			}
+
+			first := rhs.MatchingNodes.Front()
+			keyCandidate := first.Value.(*CandidateNode)
+			keyValue := keyCandidate.Node.Value
+			_, exists := newMatches.Get(keyValue)
+
+			if !exists {
+				newMatches.Set(keyValue, child.Node)
+			}
+		}
+		resultNode := &yaml.Node{Kind: yaml.SequenceNode, Tag: "!!seq"}
+		for el := newMatches.Front(); el != nil; el = el.Next() {
+			resultNode.Content = append(resultNode.Content, el.Value.(*yaml.Node))
+		}
+
+		results.PushBack(candidate.CreateChild(nil, resultNode))
+	}
+
+	return context.ChildContext(results), nil
+
+}

pkg/yqlib/operator_unique_by_test.go

@@ -0,0 +1,50 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var uniqueOperatorScenarios = []expressionScenario{
+	{
+		description:    "Unique array of scalars (string/numbers)",
+		document:   `[1,2,3,2]`,
+		expression: `unique`,
+		expected: []string{
+			"D0, P[], (!!seq)::- 1\n- 2\n- 3\n",
+		},
+	},
+	{
+		description:    "Unique nulls",
+		subdescription: "Unique works on the node value, so it considers different representations of nulls to be different",
+		document:   `[~,null, ~, null]`,
+		expression: `unique`,
+		expected: []string{
+			"D0, P[], (!!seq)::- ~\n- null\n",
+		},
+	},
+	{
+		description:    "Unique all nulls",
+		subdescription: "Run against the node tag to unique all the nulls",
+		document:   `[~,null, ~, null]`,
+		expression: `unique_by(tag)`,
+		expected: []string{
+			"D0, P[], (!!seq)::- ~\n",
+		},
+	},
+	{
+		description:    "Unique array object fields",
+		document:   `[{name: harry, pet: cat}, {name: billy, pet: dog}, {name: harry, pet: dog}]`,
+		expression: `unique_by(.name)`,
+		expected: []string{
+			"D0, P[], (!!seq)::- {name: harry, pet: cat}\n- {name: billy, pet: dog}\n",
+		},
+	},
+	
+}
+
+func TestUniqueOperatorScenarios(t *testing.T) {
+	for _, tt := range uniqueOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentScenarios(t, "Unique", uniqueOperatorScenarios)
+}